Method of grinding or polishing diamonds



Patented Sept. 10, "1929.

UNITED STATES PATENT oFrICL CLAES W. BOHAN, OI BROOKLYN, NEW YORK,ASSIGNOR TO JOYCE-ROBBED DIA- MOND TOOL DEPARTMENT, INQ, OF NEW YORK, N.Y., A. CORPORATION OF NEW YORK.

METHOD O1 GRINDING OB POLISHING DIAMONDS.

Io Drawing.

This invention relates to the art of grinding or polishing diamonds. a

In that art as now practiced it is customary to use a lapidarys wheelcomposed of suitable 5 material-that is impregnated with diamond dust.Such wheel is expensive, and by means of it plane surfaces only can beground; for instance, the girdle or equator surrounding the diamond andseparating the upper and lower parts thereof cannot be polished, and thediamond can be given only the stereotyped shape composed of facets sinceno curved sur face can be polished. This is due to the fact that whenusing the previously known lapidarys wheel the diamond can be polishedonly in a certain direction with respect to the.

grain. Thus, in grinding the facets, it is necessary not only to so turnthe diamond as to present the different facets successively, but caremust also be taken to so present the facet with respect to the directionof rotation of the wheel or lap that the grinding or pol ishing of thediamondtakes place in a certain direction with respect to the grain.Some diamonds of undoubted purity and excellence have no definitestratification or grain and can therefore not be properly polished andused for gem purposes, and these, otherwise valuable diamonds, arerendered relatively valueless and can be used only for mechanical pur'poses or they must be divided into small stones efore they can be used,if at all, for gem purposes. So also the so-called carbon diamonds,which are used only in the mechanical arts and for commercial purposesand which are harder and more amorphous than diamonds used for gempurposes, cannot be given the keen edge that is so desirable for theuses to which these diamonds are put. These conditions are well-knownand are due entirely to the inability to grind or polish diamondsotherwise than in a certain direction with respect to the grain".

The condition in the art today may therefore be summarized as follows:

1. The shape that can be given-diamonds to be used for gem purposesislimited-to the production of plane surfaces or facets; no curvedsurfaces can be polished and the girdle of the diamond cannot bepolished.

I Application flled August 5, 1921. Serial No. 490,166.

. 2. There is a great loss because of imperfect stratification or grainin diamonds that would otherwise be valuable.

3. Diamonds of an amorphous character used for mechanical purposescannot be given 65 as keen a cutting edge as is desirable.

4. The lapidarys wheel or lap heretofore used is expensive.

5. The process of grinding or polishing diamonds is slow because eachfacet must be so adjusted with respect to the rotation of the wheel orlap that grinding or polishing takes place in a certain direction withrespect to the grain. Highly skilled labor is necessary for this work.

These manifest disadvantages I have overcome by the discovery of asubstance that can be used for a lapidarys wheel and which exhibits theunexpected property of grinding or polishing diamonds regardless of thegrain, 7 or without respect to the Stratification or grain of thediamond.

This substance is known as Arkansas stone, and is a stone of suchtexture that diamonds will be cut, ground or polished without regard totheir grain or stratification. It is much cheaper than the material ofwhich the regulation lapidarys wheelis made and, by means of it, curvedsurfaces can be produced in gem diamonds; the culet of gem diamonds canbe polished; diamonds having imperfect stratification can be used forgem purposes without first subdividing them into smaller stones;diamonds used in the mechanical arts can be given a keener edge; and thespeed of cutting, grinding or polishing diamonds is materially increasedbecause of the absence of the necessitv of properly adjusting each facetwith respect to the direction of rotation of the lap.

So also the skilled labor heretoforeused is no longer necessary to carryout the process. I also find that,.if desired, the peripher of the lap,as well as its flat top surface, may be used for the purpose of cutting,grinding or polishing diamonds.

It will be understood from the foregoing that by my invention thenecessity for im- 'pregnating the lapidarys wheel with diamond dust isobviated.

I claim:

The method of grinding or polishing a, diw mond which conslsts inabrading the same, regardless of its grain, against a surface comp d ofArkansas stone.

igned at New York, in the county of New York and State of'New Ybrk, this2nd day of August, 1921.

CLAES W. BOMAN.

